1. Field of the Invention
This invention relates to a method of cleaning up contaminated soil and groundwater. More specifically, the invention relates to a method by which soil and groundwater that are contaminated with halogenated organic compounds are cleaned up by using an iron powder in combination with a reducing substance that is water-soluble and which exhibits weak acidity in water.
2. Description of the Prior Art
Soil and groundwater that are contaminated with halogenated organic compounds are conventionally cleaned up by a soil vapor evacuation (SVE) method utilizing the volatility of the contaminant or by a pump and treat (P&T) method. In these methods, the gas component of the soil or the groundwater itself is lifted to the ground level before the contaminant is treated. Therefore, a sufficient land space to treat the contaminant and treating facilities are necessary and a substantial initial investment is unavoidable for meeting this requirement. In addition, transporting the contaminant to the treating facilities on the ground level requires special means and operating cost. What is more, the effectiveness of the treatment is highly sensitive to the type of contamination, the site of contamination and its terrain.
To deal with these problems, several methods have been proposed for treating contaminants as they are kept in place. Two of such approaches are described in Japanese Patent Application Nos. 93138/1995 and 248872/1996 and based on the principle of cleaning up contaminated groundwater by establishing contact with an iron powder layer placed under the ground. These methods are effective in that they are capable of collectively removing heavy metals and halogenated organic compounds in the groundwater using an iron powder. However, the methods have had the problem that if the iron powder is used independently, the reaction rate is not fast enough to clean up the contamination within a short duration of time.
Thus, the conventional methods involving the contact of contaminants with an underground iron powder layer are an effective way to clean up the contamination at low cost as the contaminants are kept in place but, on the other hand, the reaction rate must be increased in order to complete the clean-up operation within a limited time.